Leonard p



L. P. HUTT.

CONTACTOR.

APPLICATION mep MAR. 2|. 191s.

Patevll'ted Sept. 23, 1919.

Fig. z.

Figi.

UNITED sTATEs PATENT oEEIcE.

LEONARD P..HUTT, F SCHENECTADY, NEW YORK, .ASSIGNOR T0 GENERAL ELECTRICI COMPANY, A` CORPORATION v0F NEW YORK.

.GONTACTOR Specification of Letters Patent.

Patented Sept. 23, 1919.

Application mea March 21, 191s. serial No. 223,813.

l subject of the King of Great Britain, residstarting of the motor,therefore,

ing at Schenectady, in the county of Schenectady, State of New York,have invented certain new and useful Improvements 1n Contactors, ofwhich the following isa speci- '.'fication My invention relates toelectromagnetic switches for, the control of electric circuits and hasfor its object the provision of 1mproved means whereby an electricvcircuit may be controlled in a reliable, simple and efficient manner.

My invention relates more specifically to electromagnetic switches forcontrolling electric motor circuits, one ofthe objects being to providea device of this character which will effect the automatic starting ofthe motor under the control of the motor current.

In vthe operation of electric motors it is common to both start themotor and control its speed by means of a resistance which is cut in andout of circuit. Everytime a section of resistance is cut out, thecurrent temporarily rises above normal value. The increase in speedwhich is caused by the cutting out of the section of resistanceimmediately reduces the current. During the there is a, temporary rushof current for each section of resistance which is cut out. These sec'-tions are frequently cut out of circuit by electromagnetic switcheswhich operate automatically in succession.v In order to prevent theswitches from operating too rapidly andV increasing the current beyond asafe value, various means have been devised. An ideal switch for thispurpose is onecontaining a winding which carries themotor current and aswitch member controlled thereby for cutting out the resistance, thearrangement being suchl that the switch member will not be operated tocut out the resistance until the current has fallen to a predeterminedIvalue and will assume an open position when the winding is denergized.A switch of this character was invented by Walter O. Lum and forms thesubject-matter of an application, Serial No.

611,151, led Feb. 27, 1911, assigned to the same assignee as thisapplication.

While the broad features of my device are described and claimed in thesaid Lum application, the more specific features thereof constituteimportant improvements which lend themselves to eiliciency of operationand also make the device more accurate and' positive in operation.Likewise, the improved mechanical construction of the switch renders itmore rugged and compact and likewise decreases the cost of production.

ing one form of my invention, Figure 1 is cross iece 15 of magneticmaterial connectv ing t e two branches. The member 13 is between the twomembers 12 and 14 and spaced therefrom. It is also shorter `than sof thetwo outside members and provided with a non-magnetic stop 16.forpreventing the switch lever from freezing to the memlber 12. A crosspiece 17 of magnetic material connects the outer ends of the two outsidemembers 12 and 14, leaving a space between thel end of the member 12 andcross piece 17 for themovement of the end of the switch lever. Pivotedat 18 -i'n yoke 19 of magnetic material, secured to' or forming partY ofthe core of the winding 10, is the switch -lever 20. This lever ispivoted intermediate its ends so that the lower end extends downwardinto the space between the cross piece 17 and the end of the member 13,while the upper end extends upward andfis providedvwlth a contact 2lpivoted at 22 and spring pressed by means of spring 23 to mak contact 241n a well understood manner. In

ev a wiping engagement with stationaryits normal position the switchlever 2O assumes the position shown in Fig. 1 in which it rests againsta spring pressed plunger 25. The engagement with the spring pressedplunger is made through the screw 26 mounted in bracket 27. The plungeris pressed upward by a spring 28. The plunger slides in an elongated nut29 which is chambered out to receive the spring 28. This nut is screwedinto a lug 30 which is secured to the cross piece 17 by screws 31 and ascrew 32 fits into the under side of the lug and holds the spring inplace. tension of the spring may be adjusted by turning the screw 32.Copper sleeves 33 encircle the members 12 and 111 to temporarily holdback and prevent the rise of flux in the members as hereinafterexplained.

As thus constructed and arranged, the operation of my electromagneticswitch is as follows: Normally the parts are in the position shown inFigs. 1 and 2. iVhen the winding 10 is energized above a predeterminedvalue the lower end of the switch lever will be drawn over by the pullof the magnetic member 13 into engagement with the stop 16. Temporarilythe attraction between the member 12 and the switch lever is greaterthan that between the cross member 17 and the switch lever because ofthe fact that the magnetic circuit which includes the cross piece 17 islonger than that including the magnetic member 12.Y The copper bands 33help the members 12 by temporarily holding back the flux so that thelower end of the switch lever will be pulled over by the member 12 andheld in the position shown in Fig. 3. In moving to the position shown inFig. 3, the spring 28 is compressed through the action of the screw 2Gand the plunger 27, so that in the position shown in Fig. 3, the spring28 is under strain. There are now three forces acting on the switchlever. v'iz. the magnetic force at the end ot' member 12 tending to holdthe switch lever in open position; second, a magnetic Jforce between thecross piece in the end ot-the switch lever tending to move it to closedposition; and a constant mechanical force due to the spring 28 tendingto move the switch lever to closed position, lVhen the current in themagnetizing winding 10 is decreased, the two magnetic forces acting uponthe switch lever will decrease substantially in proportion, but theforce of the spring 28 remains constant. There will, therefore, come atime when the closingforce will overcome the holding-out force and startthe switch toward closed position. Vhen the movement of the switch levertoward closed position is started, the movement will be accelerated bythe pull of the cross piece 17 due to the shortening of the air gap, andthe cross piece 17 will The l finally pull 'the switch lever stronglyand cause the contacts 21 and 2-1 to be wiped home in a well understoodmanner. The value of current in the winding l() at which the switch willoperate may be adjusted over a wide range by turning the screw 32.

Vhile I have described my invention as embodied in concrete form and asoperating in a speciiic manner in accordance with the provisions of thepatent statutes, it should be understood that I do not limit myinvention thereto as various modiiications thereof will suggestthemselves to those skilled in the art without departing from the spiritof my invention the scope of which is set forth in the annexed claims.

That Il claim as new and desire to secure by Letters Patent of theUnited States, is

1. lern-electromagnetic switch comprising a magnetic structure and amagnetizing winding therefor, a pivoted switch lever normally in openposition, a spring and means whereby said lever is moved in an openingdirection to place the spring under strain when the` inagnetizingwinding is energized by a current above a predetermined 'value and movedto closed position in response to the action of the spring and theattraction of the magnetic structure when the current drops to saidvalue.

2. An electromagnetic switch comprising a magnetic structure and amagnetizing winding therefor, a switch lever pivoted in` termediate itsends and normallyin open position, a spring, and means whereby saidlever is moved in an` opening direction by a magnetic attraction on oneend of said lever to place the spring under strain when the magnetizingwinding is energized by a current above a predetermined value and movedto closed position in response to the action of the spring and theattraction of the magnetic structure on the same end of said lever whenthe `current drops to said value.

3. An electromagnetic switch comprising a magnetizing winding and amagnetic structure therefor, having two pole pieces, a. switch levernormally in open position and forming a closing gap and a holding-outgap at said pole pieces and a spring cooperating with said lever, saidlever being movable by attraction across the holdingout gap to place thespringy under strain tending to move the switch lever to closed positionwhen the current in the Winding is above a predetermined value and actwith the closing gap-v to move the switch lever to closed position whenthe current drops to said value.

4. An electromagnetic switch comprising a magnetizing winding and amagnetic structure therefor,having two pole pieces, a pivoted switchlever normally in open position between said pole pieces and forming aclosing gap and a holding-out gap at the pole pieces, and a springarranged to be placed under strain by the movement of said switch leverin response to the attraction across the holding-out gap when theWinding is energized above a predetermined value, said lever beingmovable to closed lwhen the current drops to position .in response tothe action of the spring and the attraction at the closing gap saidvalue.

In Witness whereof 'I have hereunto set my hand this 19th day of March,1918.

LEONARD P. HUTT.

